Heat-developable light-sensitive materials often contain a base or a base precursor for the purpose of accelerating heat development. For ensuring extended storage of the light-sensitive material, base precursors which release a basic material by thermal decomposition are particularly preferred.
Typical base precursors are described in British Pat. No. 998,949. A preferred base precursor is a salt of a carboxylic acid and an organic base. Useful carboxylic acid are trichloroacetic acid and trifluoroacetic acid, and useful bases are guanidine, piperidine, morpholine, p-toluidine and 2-picoline. The guanidine trichloroacetic acid as described in U.S. Pat. No. 3,220,846 is particularly useful. The aldoneamides as described in Japanese Patent Application (OPI) No. 22625/75 (the symbol OPI as used herein means an unexamined published Japanese patent application) generate bases by pyrolysis and are used advantageously.
However, many of these base precursors require a relatively long time to produce an image or are accompanied by high fog. Moreover, these base precursors are susceptible to be affected by air or moisture and are subsequently decomposed to change the photographic properties of the light-sensitive material or impair its storage stability. The present invention aims to overcome such defects.